If I interpret the exploded drawings on the Shure KSM8 site correctly, they added a (passive) diaphragm on the bottom, which, through its specific placement, cancels certain low frequencies and puts them out-of-polarity with the same frequencies entering the active, top, diaphragm system. That is a system quite different from that used in the AKG 224 with its two active, dissimilar-sized diaphragms used to distribute and process incoming frequencies separately.
I remain skeptical of acoustic phase treatments of a sound source. That always seems to come with unpleasant sonic side effects germane to any phase shifting, or other forms of sound additions or subtractions.
Besides: why badmouth proximity effect? All good vocal mics make this effect available as an additional creative tool for the experienced vocalist.